In communication systems, signals are often transmitted from a source communication device to a target communication device via a wireless medium. These communication devices typically employ a transmitter for transmitting signals long distances via the wireless medium. In many cases, the transmitter is operated continuously, whether or not signals are being transmitted. In some cases, operating a transmitter in a continuous manner may be acceptable. However, in other cases, especially when an associated power source is limited, it may not be desirable since the communication device may not be operated continuously for a long time.
For instance, many communication devices are portable, such as cellular telephones, personal digital assistants (PDAs), handheld products, and other devices. Portable communication devices typically rely on a limited power source, such as a battery, to perform the various intended operations. A limited power source typically has a continuous use life that depends on the amount of power used by the portable device. It is generally desirable to extend the continuous use life as much as possible. Accordingly, portable communication devices are more frequently designed to consume less and less power.
One technique for operating a transmitter in a more power efficient manner is to use pulse-based modulation techniques (e.g., pulse-position modulation) to transmit signals. In such systems, a transmitter may be operated in a relatively high power mode during the transmission of a pulse signal. However, when the transmitter is not being used to transmit the pulse signal, it is operated in a relatively low power mode in order to conserve power. Similarly, in such systems, a receiver may be operated in a relatively high power mode during the reception of the pulse signal, and operated in a relatively low power mode when not receiving the signal.
In order for the receiver to know when pulses are expected to arrive, techniques for synchronizing the transmission of the pulse signal between the transmitter and receiver are typically employed. One such technique is for the transmitter to transmit pulse sequences to the receiver, which has a priori knowledge of the sequences. If the pulse sequences are transmitted in an a priori manner, the reception of the signals may be synchronized with the transmission of the signals. This allows the receiver to know when pulses are expected to be received and not received, and thus may operate in the relatively high and low power modes accordingly.